The continuing purpose of this project is to identify animal models applicable to further research into the etiology of cancer in humans. Additionally, as cases accumulate, the probability increases that domestic pets with some types of spontaneous cancers can be identified as representing the effects of low level environmental exposure to carcinogenic agents. The frequency of cancer in these animals would serve as a warning of general environmental hazards to man. The topics of current interest include: 1) environmentally influenced cancer in dogs relative to the level of industrialization in their country of residence; 2) a case-control study of 1500 cases of canine mammary neoplasms to determine risk associated with age, breed, obesity, prior ovariohysterectomy and prior benign mammary neoplasia; 3) the epidemiologic features of gastro-intestinal cancers, neoplasms of dental tissue and prostatic cancer in dogs; 4) a case control study of the long term effects of Promone in dogs; 5) a morbidity study about dogs exposed to kepone. 6) cancer morbidity amogn military working dogs compared with that in pet German Shepherds; 7) osteosarcoma in dogs; 8) splenic neoplasms in dogs.